Positive Resist Composition with Acid-Decomposable Structures

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Solution Overview

Problem

Conventional positive resist compositions face challenges in achieving fine patterns with high exposure latitude, focus latitude, and pattern collapse prevention while minimizing development defects, especially when using ArF excimer lasers, due to limitations in acid-decomposable structures and high molecular weight polymers.

Innovation Solution

A positive resist composition is developed with a resin having specific acid-decomposable structures in the main chain and side chains, along with a compound generating acid upon actinic ray exposure, to enhance solubility in alkaline developers and improve pattern formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a crosslinked polymer with acid-labile acetal skeleton in high molecular side chain is used as resist polymer, then dissolution contrast between exposed and unexposed areas is improved, but storage stability deteriorates due to very high sensitivity to acid

Engineering Contradiction:

Improvedissolution contrastVSAvoidstorage stability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent introduces different acid-decomposable structures at different locations: in the main chain ( formulas (1)-(4) ) and in the side chains (formulas (5)-(8) ). This local differentiation allows the main chain to provide storage stability while side chains enhance dissolution contrast, resolving the contradiction between these two properties.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The resist polymer is designed as a composite structure combining multiple types of acid-decomposable groups (acetal, orthoester, carbonate, carboxylate) at different positions. This composite approach enables simultaneous achievement of storage stability (from main chain structures) and dissolution contrast (from side chain structures).

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If crosslinking reaction occurs in side chain of high molecular chain using bifunctional monomer, then dissolution contrast is improved, but molecular weight distribution becomes extremely large causing poor solubility and ultrahigh molecular weight

Engineering Contradiction:

Improvedissolution contrastVSAvoidsolubility

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent segments the crosslinking function into separate components: crosslinking sites are introduced as specific recurring units (formulas (5)-(8)) distributed along the polymer chain rather than through extensive side-chain crosslinking. This segmentation prevents ultrahigh molecular weight formation while maintaining dissolution contrast.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent controls the amount of crosslinking sites by specifying that recurring units with acid-decomposable groups (formulas (5)-(8)) constitute 5-50 mol% of total recurring units. This parameter control prevents excessive crosslinking that would cause poor solubility while maintaining sufficient dissolution contrast.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If finer resist patterns are demanded, then exposure wavelength is decreased, but absorption by aromatic groups increases at shorter wavelengths making chemical amplification system insufficient

Engineering Contradiction:

Improvepattern finenessVSAvoidlight absorption

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the resist polymer by introducing specific acid-decomposable groups (formulas (1)-(8)) that have low absorption at ArF excimer laser wavelength (193 nm). This allows use of shorter wavelength for finer patterns while avoiding the absorption problem of aromatic groups.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses aliphatic hydrocarbon-based recurring units with acid-decomposable groups instead of aromatic-based resins. These aliphatic structures act as temporary protective structures that decompose upon acid generation, providing the necessary short-wavelength transparency without the persistent absorption problems of aromatic systems.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The composition achieves improved exposure latitude, focus latitude, and reduced development defects, enabling the formation of finer patterns with enhanced pattern collapse prevention.

Implementation Method 1

a resin capable of increasing solubility in an alkaline developer under action of an acid

Methodology Applied

Scientific EffectAcid decomposition: Decomposition (biological)

Implementation Method 2

a compound generating an acid when exposed to actinic rays or radiation

Methodology Applied

Scientific EffectPhotoacid generation: Photodissociation

Data Source

PatentUS7955780B2Positive resist composition and pattern forming method using the same

Publication Date: 2011.06.07 FUJIFILM CORP

AI summary

Provided is a positive resist composition using a resin having, in the polymer main chain, a specific acid decomposable structure and further having, in the side chain thereof, several specific acid decomposable groups, satisfactory in an exposure latitude, a focus latitude, and pattern collapse prevention at a high level, and having reduced development defects; and a pattern forming method.